/*******************************************************************************
 * Copyright (c) 2008, 2013 EclipseSource.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *    Ralf Sternberg - initial implementation and API
 ******************************************************************************/
package org.python.pydev.json.eclipsesource;

import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.Writer;

/**
 * Represents a JSON value. According to RFC 4627, a JSON value must be an <strong>object</strong>,
 * an <strong>array</strong>, a <strong>number</strong>, a <strong>string</strong>, or one of the
 * literal names <strong>true</strong>, <strong>false</strong>, and <strong>null</strong>.
 * <p>
 * The literal names <strong>true</strong>, <strong>false</strong>, and <strong>null</strong> are
 * represented by the constants {@link #TRUE}, {@link #FALSE}, and {@link #NULL}.
 * </p>
 * <p>
 * JSON <strong>objects</strong> and <strong>arrays</strong> are represented by the subtypes
 * {@link JsonObject} and {@link JsonArray}. Instances of these types can be created using the
 * public constructors.
 * </p>
 * <p>
 * Instances for JSON <strong>numbers</strong> and <strong>strings</strong> can be created using the
 * static factory methods {@link #valueOf(String)}, {@link #valueOf(long)}, {@link #valueOf(double)}
 * , etc.
 * </p>
 * <p>
 * In order to find out whether an instance of this class is of a certain type, the methods
 * {@link #isObject()}, {@link #isArray()}, {@link #isString()}, {@link #isNumber()} etc. can be
 * used.
 * </p>
 * <p>
 * If there is no doubt about the type of a JSON value, one of the methods {@link #asObject()},
 * {@link #asArray()}, {@link #asString()}, {@link #asInt()}, etc. can be used to get this value
 * directly in the appropriate target type.
 * </p>
 * <p>
 * This class is <strong>not supposed to be extended</strong> by clients.
 * </p>
 */
public abstract class JsonValue {

    /**
     * Represents the JSON literal <code>true</code>.
     */
    public static final JsonValue TRUE = new JsonLiteral("true");

    /**
     * Represents the JSON literal <code>false</code>.
     */
    public static final JsonValue FALSE = new JsonLiteral("false");

    /**
     * The JSON literal <code>null</code>.
     */
    public static final JsonValue NULL = new JsonLiteral("null");

    JsonValue() {
        // prevent subclasses outside of this package
    }

    /**
     * Reads a JSON value from the given reader.
     *
     * @param the
     *          reader to read the JSON value from
     * @return the JSON value that has been read
     * @throws IOException
     *           if an I/O error occurs in the reader
     * @throws ParseException
     *           if the input is not valid JSON
     */
    public static JsonValue readFrom(Reader reader) throws IOException {
        return new JsonParser(reader).parse();
    }

    /**
     * Reads a JSON value from the given string.
     *
     * @param string
     *          the string that contains the JSON value
     * @return the JSON value that has been read
     * @throws ParseException
     *           if the input is not valid JSON
     */
    public static JsonValue readFrom(String text) {
        try {
            return new JsonParser(new StringReader(text)).parse();
        } catch (IOException exception) {
            // StringReader does not throw IOException
            throw new RuntimeException(exception);
        }
    }

    /**
     * Returns a JsonValue instance that represents the given <code>long</code> value.
     *
     * @param value
     *          the value to get a JSON representation for
     * @return a JSON value that represents the given value
     */
    public static JsonValue valueOf(long value) {
        return new JsonNumber(Long.toString(value, 10));
    }

    /**
     * Returns a JsonValue instance that represents the given <code>float</code> value.
     *
     * @param value
     *          the value to get a JSON representation for
     * @return a JSON value that represents the given value
     */
    public static JsonValue valueOf(float value) {
        if (Float.isInfinite(value) || Float.isNaN(value)) {
            throw new IllegalArgumentException("Infinite and NaN values not permitted in JSON");
        }
        return new JsonNumber(Float.toString(value));
    }

    /**
     * Returns a JsonValue instance that represents the given <code>double</code> value.
     *
     * @param value
     *          the value to get a JSON representation for
     * @return a JSON value that represents the given value
     */
    public static JsonValue valueOf(double value) {
        if (Double.isInfinite(value) || Double.isNaN(value)) {
            throw new IllegalArgumentException("Infinite and NaN values not permitted in JSON");
        }
        return new JsonNumber(Double.toString(value));
    }

    /**
     * Returns a JsonValue instance that represents the given string.
     *
     * @param string
     *          the string to get a JSON representation for
     * @return a JSON value that represents the given string
     */
    public static JsonValue valueOf(String string) {
        return string == null ? NULL : new JsonString(string);
    }

    /**
     * Returns a JsonValue instance that represents the given <code>boolean</code> value.
     *
     * @param value
     *          the value to get a JSON representation for
     * @return a JSON value that represents the given value
     */
    public static JsonValue valueOf(boolean value) {
        return value ? TRUE : FALSE;
    }

    /**
     * Detects whether this value represents a JSON object. If this is the case, this value is an
     * instance of {@link JsonObject}.
     *
     * @return <code>true</code> if this value is an instance of JsonObject
     */
    public boolean isObject() {
        return false;
    }

    /**
     * Detects whether this value represents a JSON array. If this is the case, this value is an
     * instance of {@link JsonArray}.
     *
     * @return <code>true</code> if this value is an instance of JsonArray
     */
    public boolean isArray() {
        return false;
    }

    /**
     * Detects whether this value represents a JSON number.
     *
     * @return <code>true</code> if this value represents a JSON number
     */
    public boolean isNumber() {
        return false;
    }

    /**
     * Detects whether this value represents a JSON string.
     *
     * @return <code>true</code> if this value represents a JSON string
     */
    public boolean isString() {
        return false;
    }

    /**
     * Detects whether this value represents a boolean value.
     *
     * @return <code>true</code> if this value represents either the JSON literal
     *         <code>true</code> or <code>false</code>
     */
    public boolean isBoolean() {
        return false;
    }

    /**
     * Detects whether this value represents the JSON literal <code>true</code>.
     *
     * @return <code>true</code> if this value represents the JSON literal
     *         <code>true</code>
     */
    public boolean isTrue() {
        return false;
    }

    /**
     * Detects whether this value represents the JSON literal <code>false</code>.
     *
     * @return <code>true</code> if this value represents the JSON literal
     *         <code>false</code>
     */
    public boolean isFalse() {
        return false;
    }

    /**
     * Detects whether this value represents the JSON literal <code>null</code>.
     *
     * @return <code>true</code> if this value represents the JSON literal
     *         <code>null</code>
     */
    public boolean isNull() {
        return false;
    }

    /**
     * Returns this JSON value as {@link JsonObject}, assuming that this value represents a JSON
     * object. If this is not the case, an exception is thrown.
     *
     * @return a JSONObject for this value
     * @throws UnsupportedOperationException
     *           if this value is not a JSON object
     */
    public JsonObject asObject() {
        throw new UnsupportedOperationException("Not an object: " + toString());
    }

    /**
     * Returns this JSON value as {@link JsonArray}, assuming that this value represents a JSON
     * array. If this is not the case, an exception is thrown.
     *
     * @return a JSONArray for this value
     * @throws UnsupportedOperationException
     *           if this value is not a JSON array
     */
    public JsonArray asArray() {
        throw new UnsupportedOperationException("Not an array: " + toString());
    }

    /**
     * Returns this JSON value as an <code>int</code> value, assuming that this value represents a
     * JSON number that can be interpreted as Java <code>int</code>. If this is not the case, an
     * exception is thrown.
     * <p>
     * To be interpreted as Java <code>int</code>, the JSON number must neither contain an exponent
     * nor a fraction part. Moreover, the number must be in the <code>Integer</code> range.
     * </p>
     *
     * @return this value as <code>int</code>
     * @throws UnsupportedOperationException
     *           if this value is not a JSON number
     * @throws NumberFormatException
     *           if this JSON number can not be interpreted as <code>int</code> value
     */
    public int asInt() {
        throw new UnsupportedOperationException("Not a number: " + toString());
    }

    /**
     * Returns this JSON value as a <code>long</code> value, assuming that this value represents a
     * JSON number that can be interpreted as Java <code>long</code>. If this is not the case, an
     * exception is thrown.
     * <p>
     * To be interpreted as Java <code>long</code>, the JSON number must neither contain an exponent
     * nor a fraction part. Moreover, the number must be in the <code>Long</code> range.
     * </p>
     *
     * @return this value as <code>long</code>
     * @throws UnsupportedOperationException
     *           if this value is not a JSON number
     * @throws NumberFormatException
     *           if this JSON number can not be interpreted as <code>long</code> value
     */
    public long asLong() {
        throw new UnsupportedOperationException("Not a number: " + toString());
    }

    /**
     * Returns this JSON value as a <code>float</code> value, assuming that this value represents a
     * JSON number. If this is not the case, an exception is thrown.
     * <p>
     * If the JSON number is out of the <code>Float</code> range, {@link Float#POSITIVE_INFINITY} or
     * {@link Float#NEGATIVE_INFINITY} is returned.
     * </p>
     *
     * @return this value as <code>float</code>
     * @throws UnsupportedOperationException
     *           if this value is not a JSON number
     */
    public float asFloat() {
        throw new UnsupportedOperationException("Not a number: " + toString());
    }

    /**
     * Returns this JSON value as a <code>double</code> value, assuming that this value represents a
     * JSON number. If this is not the case, an exception is thrown.
     * <p>
     * If the JSON number is out of the <code>Double</code> range, {@link Double#POSITIVE_INFINITY} or
     * {@link Double#NEGATIVE_INFINITY} is returned.
     * </p>
     *
     * @return this value as <code>double</code>
     * @throws UnsupportedOperationException
     *           if this value is not a JSON number
     */
    public double asDouble() {
        throw new UnsupportedOperationException("Not a number: " + toString());
    }

    /**
     * Returns this JSON value as String, assuming that this value represents a JSON string. If this
     * is not the case, an exception is thrown.
     *
     * @return the string represented by this value
     * @throws UnsupportedOperationException
     *           if this value is not a JSON string
     */
    public String asString() {
        throw new UnsupportedOperationException("Not a string: " + toString());
    }

    /**
     * Returns this JSON value as a <code>boolean</code> value, assuming that this value is either
     * <code>true</code> or <code>false</code>. If this is not the case, an exception is thrown.
     *
     * @return this value as <code>boolean</code>
     * @throws UnsupportedOperationException
     *           if this value is neither <code>true</code> or <code>false</code>
     */
    public boolean asBoolean() {
        throw new UnsupportedOperationException("Not a boolean: " + toString());
    }

    /**
     * Writes the JSON representation for this object to the given writer.
     *
     * @param writer
     *          the writer to write this value to
     * @throws IOException
     *           if an I/O error occurs in the writer
     */
    public void writeTo(Writer writer) throws IOException {
        write(new JsonWriter(writer));
    }

    /**
     * Returns the JSON string for this value in its minimal form, without any additional whitespace.
     * The result is guaranteed to be a valid input for the method {@link #readFrom(String)} and to
     * create a value that is <em>equal</em> to this object.
     *
     * @return a JSON string that represents this value
     */
    @Override
    public String toString() {
        StringWriter stringWriter = new StringWriter();
        JsonWriter jsonWriter = new JsonWriter(stringWriter);
        try {
            write(jsonWriter);
        } catch (IOException exception) {
            // StringWriter does not throw IOExceptions
            throw new RuntimeException(exception);
        }
        return stringWriter.toString();
    }

    public String toPrettyString() {
        StringWriter stringWriter = new StringWriter();
        PrettyJsonWriter jsonWriter = new PrettyJsonWriter(stringWriter);
        try {
            write(jsonWriter);
        } catch (IOException exception) {
            // StringWriter does not throw IOExceptions
            throw new RuntimeException(exception);
        }
        return stringWriter.toString();
    }

    /**
     * Indicates whether some other object is "equal to" this one according to the contract specified
     * in {@link Object#equals(Object)}.
     * <p>
     * Two JsonValues are considered equal if and only if they represent the same JSON text. As a
     * consequence, two given JsonObjects may be different even though they contain the same set of
     * names with the same values, but in a different order.
     * </p>
     *
     * @param object
     *          the reference object with which to compare
     * @return true if this object is the same as the object argument; false otherwise
     */
    @Override
    public boolean equals(Object object) {
        return super.equals(object);
    }

    protected abstract void write(JsonWriter writer) throws IOException;

}
